This invention relates to safety devices for pressure vessels, particularly to such devices incorporating reverse buckling discs.
A reverse buckling disc comprises a concave-convex dome portion surrounded by an annular or substantially annular flange portion, and it is established practice to utilise such a disc in conjunction with one or more knife blades to release excessive pressure that may build up inside an associated vessel.
In such an arrangement, the flange portion of the disc is commonly securely clamped between a pair of opposed support means with the convex side of the dome portion facing the pressure vessel, the or each knife blade being located to the concave side of the dome portion of the disc. When a critical pressure is reached in the vessel, the dome portion reverses into contact with the knife blades which rupture and cut the dome portion into segments so that the pressure within the vessel is relieved.
With certain pressure and size combinations, and particularly at high pressures, the segments formed by the knife blades on reversal of discs of the above type have a pronounced tendency to tear along a line defined by the innermost edge of the outlet support means, which line corresponds with the intersection between the dome portion and the flange portion of the disc.
Clearly such tearing can result in loose pieces of metal flying about in the outlet bore and can cause many consequential problems.
It has been proposed to solve this problem by providing the annular outlet member of the disc supporting means with a rounded shoulder which projects radially inwardly of the bore through the inlet member of said means--i.e. radially inwardly of the bore to be monitored. With such an arrangement, and on reversal of the dome portion of the disc, the presence of said shoulder prevents the undesired tearing of the segments formed by the knife blades.